Recent trials test road markings

After a lot of research, newly developed road marker products are lasting longer on road pavement surfaces laid by roading contractors in this country. Richard Silcock explains.

IN A THREE-YEAR research project that originally started back in 2010, the NZ Transport Agency has been testing a range of products used for marking road centre lines, directional arrows and compulsory stop lines etc.

The research has shown that a number of newly developed road marker products, which were provided by various manufacturers and suppliers for the research project, are performing well and are generally lasting longer on the predominate types of road pavement surfaces laid by roading contractors in this country.

A 150-metre stretch of road at Silverstream in the Hutt Valley, north of Wellington was originally selected as the field trial site and horizontal strips or lines of the various types of road marking products under review were applied to the pavement to test their durability, longevity, visibility and composition. However, due to some misunderstanding the test area was resurfaced by the local council midway through the three-year trial period.

In November 2013 the trial was resurrected, this time on a section of SH1 south of Te Horo on the Kapiti Coast as well as at the previous site at Silverstream.

For this ‘second’ trial five different manufacturers and suppliers provided 68 road marking products ranging from paint to adhesive tape, all of which had to comply with the internationally approved road marking colour palette of yellow and white.

Each product was applied on two different types of road surface for this trial, asphaltic concrete at Silverstream and chip-seal at Te Horo. Trialling of the products on two different road surfaces was seen as important as it helps to ascertain how each product performs on each surface.

Four test strips of each product were applied to the road surface, two on a ‘virgin’ road surface and two over markings that had been applied several months earlier to ascertain if this increased the longevity and visibility of the markings.

Each of the product strips was placed across the width of a traffic lane to ensure maximum vehicle crossings and to accelerate the testing and wearing process so that the trial results could be ascertained sooner.

The research and technical work for the project was carried out for the Transport Agency by the Opus Research laboratory in Petone, which set up the trial sites and carried out the field inspections and subsequent analysis.

Each strip was checked after 24 hours of the products being laid, and then after 500,000 vehicles had passed over them, after one million vehicles, and again in October 2014 when it was calculated 1.5 million vehicles would have passed over with most of the research analysis taking place at the same time.

The marker strips showing the best results earlier in the trial period were again inspected in September last year after an estimated five million vehicles would have passed over.

The products were all laid at the same time so that the performance of each could be compared following their exposure under equal conditions and checked against the trial criteria of skid resistance, visibility in both daylight and at night, wear from vehicle tyres, and deterioration from weather, colour fading or darkening.

“This research has enabled us to see how safe, visible and durable each of the 68 products performed over a period of time, under differing weather conditions, on differing pavement surfaces and traffic counts,” a Transport Agency spokesperson said.

“We carried out this research as the road marking products are just as important as the reason for the road markings themselves. The product has to be bright enough to be seen in the daylight and at night in both wet or dry weather conditions and be sufficiently durable to withstand high traffic pass-over volumes over a reasonable period.”

As a result of this trail a 3M product was found to be the best overall in meeting the performance criteria and was shown to be the most easily applied, was durable and resistant to skid and showed good visibility over the trial period.

The trials also found that product applied over the top of existing road markings increased its longevity and visibility.

The Transport Agency last carried out similar research some 10-15 years ago prior to this trial and is pleased that the newer products are lasting longer even with the increase in traffic volumes.

The agency maintains a list of specifications for road marking products along with a list of products that have been trialled successfully under New Zealand conditions and are approved for use on the state highway network as of August 2017.

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